Efficient wind turbine blades, wind turbine blade structures, and associated systems and methods of manufacture, assembly and use

ABSTRACT

Wind turbine systems and methods are disclosed herein. A representative system includes a wind turbine blade having an inner region that has an internal load-bearing truss structure, and an outer region that has an internal, non-truss, load-bearing structure. In particular embodiments, the truss structure can include a triangular arrangement of spars, and/or can include truss attachment members that connect components of the truss without the use of holes in the spars. Spars can be produced from a plurality of pultruded composite members laminated together in longitudinally extending portions. The longitudinally extending portions can be connected at joints that interleave projections and recesses of each of the spar portions. The blades can include fan-shaped transitions at a hub attachment portion, formed by laminated layers and/or a combination of laminated layers and transition plates.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/154,384, filed Jun. 6, 2011, entitled “EFFICIENT WINDTURBINE BLADES, WIND TURBINE BLADE STRUCTURES, AND ASSOCIATED SYSTEMSAND METHODS OF MANUFACTURE, ASSEMBLY AND USE,” which is a continuationof International Application Serial No. PCT/US2009/066875, filed Dec. 4,2009, entitled “EFFICIENT WIND TURBINE BLADES, WIND TURBINE BLADESTRUCTURES, AND ASSOCIATED SYSTEMS AND METHODS OF MANUFACTURE, ASSEMBLYAND USE,” which claims priority to the following U.S. Provisional PatentApplications, each of which is incorporated herein in its entirety byreference: 61/120,338, filed Dec. 5, 2008; 61/220,187, filed Jun. 24,2009; and 61/271,179, filed Jul. 17, 2009.

TECHNICAL FIELD

The present disclosure is directed generally to efficient wind turbineblades and wind turbine blade structures, including lightweight,segmented and/or otherwise modular wind turbine blades, and associatedsystems and methods of manufacture, assembly, and use.

BACKGROUND

As fossil fuels become scarcer and more expensive to extract andprocess, energy producers and users are becoming increasingly interestedin other forms of energy. One such energy form that has recently seen aresurgence is wind energy. Wind energy is typically harvested by placinga multitude of wind turbines in geographical areas that tend toexperience steady, moderate winds. Modern wind turbines typicallyinclude an electric generator connected to one or more wind-driventurbine blades, which rotate about a vertical axis or a horizontal axis.

In general, larger (e.g., longer) wind turbine blades produce energymore efficiently than do short blades. Accordingly, there is a desire inthe wind turbine blade industry to make blades as long as possible.However, long blades create several challenges. For example, long bladesare heavy and therefore have a significant amount of inertia, which canreduce the efficiency with which the blades produce energy, particularlyat low wind conditions. In addition, long blades are difficult tomanufacture and in many cases are also difficult to transport.Accordingly, a need remains for large, efficient, lightweight windturbine blades, and suitable methods for transporting and assemblingsuch blades.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic, isometric illustration of a windturbine system having blades configured in accordance with an embodimentof the disclosure.

FIG. 2A is a partially schematic, side elevation view of a wind turbineblade having a hybrid truss/non-truss structure in accordance with anembodiment of the disclosure.

FIG. 2B is an enlarged illustration of a portion of the wind turbineblade shown in FIG. 2A.

FIGS. 2C-2F are schematic cross-sectional illustrations of wind turbineblade portions having truss structures in accordance with severalembodiments of the disclosure.

FIG. 3 is a partially schematic, isometric illustration of a portion ofa wind turbine blade having three spars that form part of a trussstructure in accordance with an embodiment of the disclosure.

FIG. 4 is a partially schematic, isometric illustration of a portion ofa wind turbine blade having a non-truss internal structure in accordancewith an embodiment of the disclosure.

FIG. 5A is a partially schematic, isometric illustration of an internalportion of a wind turbine blade having truss attachment membersconfigured in accordance with an embodiment of the disclosure.

FIGS. 5B-5C are enlarged isometric illustrations of a truss attachmentmember configured in accordance with an embodiment of the disclosure.

FIGS. 5D-5F illustrate several views of an internal portion of a windturbine blade having a truss structure secured at least in part withtruss attachment members configured in accordance embodiments of thedisclosure.

FIG. 6A is a partially schematic, side elevation view of a spar havingmultiple portions, each with layers that terminate at staggeredpositions to form a non-monotonically varying bond line.

FIG. 6B is an illustration of an embodiment of the structure shown inFIG. 6A with clamps positioned to prevent or limit delamination inaccordance with an embodiment of the disclosure.

FIG. 6C is an enlarged illustration of a portion of the spar shown inFIG. 6B.

FIGS. 6D-6G are partially schematic illustrations of spars having jointsconfigured in accordance with further embodiments of the disclosure.

FIG. 7A is a partially schematic, isometric illustration of a sparhaving layers that fan out at a hub attachment region in accordance withan embodiment of the disclosure.

FIG. 7B is a partially schematic, isometric illustration of a sparconnected to fan-shaped transition plates at a hub attachment region inaccordance with another embodiment of the disclosure.

FIG. 8A is a partially schematic, side elevation view of a wind turbineblade structure subassembly configured in accordance with an embodimentof the disclosure, and FIG. 8B is an enlarged, partially schematic endview of a rib from the subassembly of FIG. 8A.

FIGS. 9A-9C are partially schematic, not-to-scale isometric views ofinboard, midboard, and outboard spar portions configured in accordancewith embodiments of the disclosure.

FIGS. 9D and 9E include partially schematic, cut-away side elevationviews of the inboard and midboard spar portions of FIGS. 9A and 9B,respectively, and FIG. 9F is a partially schematic, side elevation viewof a joint between adjacent end portions of the inboard spar portion andthe midboard spar portion of FIGS. 9A and 9B, configured in accordancewith several embodiments of the disclosure.

FIGS. 10A and 10C-10E are a series of partially schematic, sideelevation views of a portion of a blade subassembly illustrating variousstages in a method of manufacturing a blade spar in accordance with anembodiment of the disclosure, and FIG. 10B is an enlarged end view of aportion of a representative rib illustrating another stage in the methodof blade manufacture.

FIGS. 11A-11C are an enlarged isometric view of a portion of a windturbine blade structure, an end view of a representative rib, and anisometric view of the wind turbine blade structure, respectively,illustrating various aspects of a spar manufactured in accordance withan embodiment of the disclosure.

FIG. 12A is an isometric view of a compressing apparatus configured inaccordance with an embodiment of the disclosure, and FIG. 12B is apartially exploded isometric view of the compressing apparatus of FIG.12A.

FIGS. 13A and 13B are enlarged isometric views of opposing end portionsof a first tool portion of the compressing apparatus of FIGS. 12A and12B.

FIG. 14A is an isometric view of a second tool portion of thecompressing apparatus of FIGS. 12A and 12B, and FIG. 14B is a partiallyexploded isometric view of the second tool portion of FIG. 14A.

FIG. 15 is an enlarged, cross-sectional end view of a laminated bladespar being compressed by the compressing apparatus of FIGS. 12A and 12Bduring an adhesive curing cycle in accordance with an embodiment of thedisclosure.

FIG. 16 is a partially schematic isometric view of a lay-up toolillustrating various stages in a method of manufacturing a wind turbineblade spar in accordance with another embodiment of the disclosure.

DETAILED DESCRIPTION

The present disclosure is directed generally to efficient wind turbineblades, wind turbine blade spars and other structures, and associatedsystems and methods of manufacture, assembly, and use. Several detailsdescribing structures and/or processes that are well-known and oftenassociated with wind turbine blades are not set forth in the followingdescription to avoid unnecessarily obscuring the description of thevarious embodiments of the disclosure. Moreover, although the followingdisclosure sets forth several embodiments, several other embodiments canhave different configurations or different components than thosedescribed in this section. In particular, other embodiments may haveadditional elements or may lack one or more of the elements describedbelow with reference to FIGS. 1-16. In FIGS. 1-16, many of the elementsare not drawn to scale for purposes of clarity and/or illustration.

FIG. 1 is a partially schematic, isometric illustration of an overallsystem 100 that includes a wind turbine 103 having blades 110 configuredin accordance with an embodiment of the disclosure. The wind turbine 103includes a tower 101 (a portion of which is shown in FIG. 1), a housingor nacelle 102 carried at the top of the tower 101, and a generator 104positioned within the housing 102. The generator 104 is connected to ashaft or spindle having a hub 105 that projects outside the housing 102.The blades 110 each include a hub attachment portion 112 at which theblades 110 are connected to the hub 105, and a tip 121 positionedradially or longitudinally outwardly from the hub 105. In an embodimentshown in FIG. 1, the wind turbine 103 includes three blades connected toa horizontally-oriented shaft. Accordingly, each blade 110 is subjectedto cyclically varying loads as it rotates between the 12:00, 3:00, 6:00and 9:00 positions, because the effect of gravity is different at eachposition. In other embodiments, the wind turbine 103 can include othernumbers of blades connected to a horizontally-oriented shaft, or thewind turbine 103 can have a shaft with a vertical or other orientation.In any of these embodiments, the blades 110 can have structuresconfigured in accordance with the arrangements described in furtherdetail below with reference to FIGS. 2A-16.

FIG. 2A is a partially schematic, partially cut-away illustration of oneof the blades 110 shown in FIG. 1. The blade 110 extends outwardly in aradial or longitudinal direction from an inner region 113 that includesthe hub attachment portion 112, to an outer region 114 that includes thetip 121. The hub attachment portion 112 can include one or more hubattachment elements, e.g., a ring with a bolt circle, one or morebearings, fasteners, and/or other elements. The internal structure ofthe blade 110 can be different at the inner region 113 than at the outerregion 114. For example, the inner region 113 can include a trussstructure 140 formed from a plurality of longitudinally or radiallyextending beams or spars 170, chordwise extending ribs 142, and trussmembers 143 connected among the spars 170 and the ribs 142. The trussstructure 140 can be surrounded by a skin 115 (most of which is removedin FIG. 2A) that presents a smooth, aerodynamic surface to the windduring operation. The outer region 114 can include a non-trussstructure, which will be described in further detail later withreference to FIG. 4. As used herein, the term “truss structure” refersgenerally to a load-bearing structure that includes generally straight,slender members forming closed shapes or units (e.g., triangular units).The term “non-truss structure” refers generally to a load-bearingstructure having an arrangement that does not rely on, or does notprimarily rely on, straight slender members forming closed-shape unitsfor strength. Such structures may include, for example, monocoque andsemi-monocoque structures. Accordingly, the skin 115 of the inner region113 is generally non-load bearing, and the skin 115 at the outer region114 is load bearing.

In a particular aspect of an embodiment shown in FIG. 2A, the blade 110includes three segments 116, shown as a first segment 116 a, a secondsegment 116 b, and a third segment 116 c. The first and second segments116 a, 116 b can each have the truss structure 140 described above, andthe third segment 116 c can have a non-truss structure. Accordingly, theblade 110 can have a truss structure for the inner two-thirds of itsspan, and a non-truss structure for the outer one-third. In otherembodiments, these values can be different, depending, for example, onthe size, shape and/or other characteristics of the blade 110. Forexample, in one embodiment, the truss structure 140 extends outwardlyover a majority of the span or length of the blade 110, but by an amountless than or greater than two-thirds of the length. The segments 116 canbe manufactured individually and then connected to each other at amanufacturing facility, or at an end user installation site. Forexample, the segments 116 can each be sized to fit in a 53-foot or othersuitably sized container for shipment. In other embodiments, one or moreof the segments (e.g., the first segment 116 a and the second segment116 b) can be built entirely at the installation site.

In still further embodiments, the blade 110 can include other numbers ofsegments 116 (e.g., two or more segments). In any of these embodiments,individual segments 116 can include ribs 142, truss members 143, andportions of the spars 170 that extend for the length of the segment 116.The segments 116 can be joined to each other by joining adjacent sparportions, e.g., as discussed later with reference to FIGS. 6A-6C and8A-16. For example, the first segment 116 a can include one or morefirst spar segments that are joined to corresponding second sparsegments of the second segment 116 b. The resulting joined spars canextend along corresponding generally smooth, continuous longitudinalaxes. In any of these embodiments, the skin 115 can be laid up on thetruss structure 140 with or without forming a joint at the interfacebetween adjacent segments 116. For example, the spar portions can bejoined at a location between two neighboring ribs 142, and a relativelysmall panel of skin 115 can be laid over the spar joint and the twoneighboring ribs 142. The neighboring ribs 142 can be spaced apart byabout one meter in one embodiment, and by other values in otherembodiments. Larger panels of the skin 115 can be laid inboard andoutboard of the small panel. In another embodiment, the skin 115 canhave no spanwise joints and can be laid up as a continuous element. Inany of these embodiments, the skin 115 can be attached (e.g., adhesivelybonded or ultrasonically bonded) to the ribs 142 alone, or to the ribs142 and the spars 170. In any of these embodiments, the truss structure140 can serve as primary structure for carrying shear and bending loadsin the blade 110.

FIG. 2B is a partially schematic, isometric illustration of a portion ofthe blade 110 shown in FIG. 2A, taken at a location where the internalstructure of the blade 110 is a truss structure 140. Accordingly, thetruss structure 140 can include multiple spars 170 (four are shown inFIG. 2B) attached to spaced-apart ribs 142. Truss members 143 can beconnected between neighboring spars 170, for example, using techniquesdescribed later with reference to FIGS. 5A-5F.

FIGS. 2C-2F are schematic, cross-sectional illustrations of blades 110having truss arrangements configured in accordance with a variety ofembodiments. FIG. 2C illustrates a blade 110 having four spars 170positioned in a generally rectangular arrangement. FIG. 2D illustrates ablade 110 having six spars 170, including four spars 170 positioned in agenerally rectangular arrangement, and two additional spars 170, onepositioned forward of the generally rectangular arrangement, and onepositioned aft of the generally rectangular arrangement. FIG. 2Eillustrates a blade 110 having four spars 170 positioned in a generallydiamond-shaped arrangement, and FIG. 2F illustrates a blade 110 havingthree spars 170 positioned in a triangular arrangement. In otherembodiments, the blade 110 can include spars 170 having otherarrangements.

FIG. 3 is an isometric illustration of an internal portion of a blade110 having a truss structure 140 that includes a triangular arrangementof spars 170, generally similar to that shown in FIG. 2F. The blade 110extends in a longitudinal radial, or spanwise direction along a spanwiseaxis S, and extends fore and aft along a transverse chordwise axis C.Accordingly, the blade 110 can have a forward leading edge region 117with a leading edge 117 a and an aft trailing edge region 118 with atrailing edge 118 a. The thickness of the blade 110 can be measuredrelative to a thickness axis T transverse to both the spanwise axis Sand the chordwise axis C.

In a particular embodiment shown in FIG. 3, the blade 110 can includethree spars 170, including a first spar 170 a and a second spar 170 b,both positioned at the leading edge region 117 and/or toward the leadingedge 117 a and spaced apart from each other along the thickness axis T.The blade 110 can further include a third spar 170 c positioned at thetrailing edge region 118 and/or toward the trailing edge 118 a andspaced apart from both the first spar 170 a and the second spar 170 balong the chordwise axis C. Each of the spars 170 a-170 c is attached toa plurality of ribs 142 (one of which is visible in FIG. 3) which are inturn spaced apart from each other along the spanwise axis S. Each of thespars 170 a-c can have a generally rectangular cross-section. Theforward spars 170 a, 170 can have a chordwise dimension greater than athickness dimension, and the aft spar 170 c can have a thicknessdimension greater than a chordwise dimension. The third spar 170 c canextend over a majority of the thickness dimension of the blade 110 andin a particular embodiment, can extend over the entirety or nearly theentirety of the thickness dimension. For example, the third spar 170 ccan have a dimension in the thickness direction that is about the sameas the dimension of the rib 142 in the thickness direction.

One feature of the arrangement shown in FIG. 3 is that it can include asingle spar (the third spar 170 c) at the trailing edge region 118. Forexample, the truss structure 140 can include only three longitudinallyextending spars 170 at any given longitudinal location, with only one ofthe spars 170 at the trailing edge region 118. This arrangement canallow the third spar 170 c to be positioned a greater chordwise distanceaway from the first and second spars 170 a, 170 b than some arrangementsthat include four spars (e.g., the arrangement shown in FIGS. 2B-2C). Byspacing the third spar 170 c further away from the first and secondspars 170 a, 170 b, the ability of the truss structure 140 to handlelarge loads in the chordwise direction C is enhanced. This can beparticularly important for wind turbine blades mounted to a horizontalshaft because such blades are subjected to significant gravity loads inthe chordwise direction C when the blades are at the 3:00 and 9:00positions described above with reference to FIG. 1. Accordingly, it isexpected that this arrangement may be lighter and/or better able towithstand significant loads in the chordwise direction C than at leastsome arrangements having four spars. At the same time, it is expectedthat this arrangement will be simpler, lighter and/or less costly thanarrangements that include more than four spars e.g., the arrangementdescribed above with reference to FIG. 2D.

The internal structural components described above can be manufacturedfrom suitable composite and/or non-composite materials. For example, thespars 170 can be formed from a laminate of layers that each includeunidirectional fiberglass, carbon fibers, and/or other fibers in amatrix of suitable thermoset and/or thermoplastic resins. The fibers canbe oriented generally parallel to the spanwise axis S over most of thelength of the blade 110, and can have other orientations at specificlocations, as described further below with reference to FIGS. 6A-7A. Inother embodiments, composite spars can also be fabricated by infusion,prepreg, pultrusion, or press molding. In still further embodiments, thespars 170 can be formed from metallic materials, including machined,forged or cast alloys, metallic laminates, sandwich structures, as wellas metal/composite hybrids (e.g., composite facesheets with metalliccore, e.g., honeycomb core), etc. The truss members 143 can be formedfrom aluminum (e.g., 2024-T6 aluminum) or another suitable metal,composite, or other material. The ribs 142 can be formed from acomposite of fiberglass and foam or balsa, e.g., a balsa core sandwichedbetween fiberglass faceplates. In other embodiments, the ribs 142 can beformed from fiberglass alone, without a foam or balsa core, or the ribs142 can be formed with other techniques and/or components. For example,the ribs 142 can have a corrugated or beaded construction. The ribs 142can be formed from a single panel, or two spaced apart panels, with nocore structure between the two panels. The ribs 142 can also be madefrom metal; from composite materials such as fiberglass, carbon fibers,and/or other fibers in a matrix of thermoset and/or thermoplastic;and/or from (unreinforced) plastic materials (e.g., resin withoutfibers). For example, composite ribs can be fabricated by wetlamination, infusion, prepreg, sprayed chopped fiber, press molding,vacuum forming, and/or other suitable mass production techniques.

FIG. 4 is a partially schematic illustration of a portion of the windturbine blade 110 located at the outer region 114 described above withreference to FIG. 2A. In this embodiment, the internal structure of thewind turbine blade 110 at the outer region 114 is not a truss structure.For example, the structure can instead include a relatively thin web 119oriented generally parallel to the thickness axis T and extending alongthe spanwise axis S. The web 119 can be connected to or formedintegrally with flanges 120 extending in the chordwise direction C.Spanwise-extending spars 470 a, 470 b are attached to each of theflanges 120 and are in turn connected to a skin 115, a portion of whichis shown in FIG. 4A. In one embodiment, the structure can includespaced-apart ribs 142 positioned in the trailing edge region 118. Inother embodiments, such ribs 142 can extend into the leading edge region117 as well. The skin 115 can be formed from afiberglass-balsa-fiberglass sandwich, or a fiberglass-foam-fiberglasssandwich. In other embodiments, the skin 115 can be formed fromcomposite materials fabricated by wet lamination, infusion, prepreg,sprayed chopped fiber, press molding, vacuum forming, and/or other massproduction techniques. The skin 115 can have the same construction inboth the outer region 114 shown in FIG. 4, and the inner region 113shown in FIG. 3. The ribs 142 can have a similar construction. The web119 and flanges 120 can be formed from fiberglass, e.g., unidirectionalfiberglass. In other embodiments, any of the foregoing components can beformed from other suitable materials. The spars 470 a, 470 b located inthe outer region 114 can be bonded to corresponding spars at the innerregion 113 (FIG. 2A) using a variety of techniques including, but notlimited to, those described later with reference to FIGS. 6A-6C and8A-16. In any of these embodiments, the spars 470 a, 470 b located inthe outer region 114 can extend along the same generally smooth,continuous longitudinal axes as the counterpart spars in the innerregion 113 to efficiently transfer loads from the outer region 114 tothe inner region 113.

One feature of the arrangement described above with reference to FIGS.2A-4 is that the blade 110 can include both truss and non-truss internalstructures. An advantage of this arrangement is that it can be morestructurally efficient than a design that includes either a trussstructure alone or a non-truss structure alone. For example, the trussstructure can be used at the inner region 113 (e.g., near the hub) wherebending loads are higher than they are near the tip 111, and where theblade 110 is relatively thick. At the outer region 114, the non-trussstructure can be easier to integrate into this relatively thin portionof the blade 110. The non-truss structure in this region is alsoexpected to be more structurally efficient than a truss structure, whichtends to lose efficiency when the aspect ratio of the closed shapesformed by the truss members becomes large.

FIG. 5A is a partially schematic, isometric illustration of a portion ofa representative truss structure 140 configured in accordance with aparticular embodiment of the disclosure. In this embodiment, the trussstructure 140 includes three spars 170, identified as a first spar 170a, a second spar 170 b and a third spar 170 c. In other embodiments, thetruss structure 140 can have other numbers and/or arrangements of spars170. In any of these embodiments, the truss structure 140 can includetruss members 143 and ribs 142, in addition to the spars 170. Trussattachment members 150 can connect the truss members 143 to the spars170. For example, truss members 143 can include a first attachmentfeature 151 a (e.g., a first mounting hole) that is aligned with asecond attachment feature 151 b (e.g., a second corresponding mountinghole) carried by the truss attachment member 150. When the twoattachment features 151 a, 151 b include corresponding holes, they canbe connected via an additional fastening member 157, e.g., a rivet orthreaded fastener. In other embodiments, the attachment features 151 a,151 b can be connected directly to each other, for example, if onefeature includes an expanding prong and the other includes acorresponding hole.

FIG. 5B illustrates a representative portion of the truss structure 140described above with reference to FIG. 5A. As shown in FIG. 5B, arepresentative truss attachment member 150 is positioned along thesecond spar 170 b so as to receive and attach to multiple truss members143. Each of the truss members 143 can include a slot 145 which receivesa flange-shaped truss attachment portion 154 of the truss attachmentmember 150. In this embodiment, the attachment features 151 a, 151 binclude corresponding holes 158 a, 158 b that are connected with thefastening members 157 described above with reference to FIG. 5A.

FIG. 5C is an enlarged isometric illustration of one of the trussattachment members 150 shown in FIGS. 5A-5B. In this embodiment, thetruss attachment member 150 includes a spar attachment portion 152 (e.g.having a channel 153 in which the corresponding spar 170 is positioned),and one or more truss attachment portions 154 (two are shown in FIG.5B). The truss attachment portions 154 can have a flat, flange-typeshape in which the second attachment features 151 b (e.g., the mountingholes 158 b) are positioned. In a particular embodiment shown in FIG.5B, the truss attachment member 150 is formed from two complementarycomponents or pieces: a first component or piece 156 a and secondcomponent or piece 156 b. The first piece 156 a includes two firstflange portions 155 a, and the second piece 156 b includes two secondflange portions 155 b. When the two pieces 156 a, 156 b are placedtogether, the first flange portions 155 a mate with corresponding secondflange portions 155 b to form two flange pairs, each of which forms oneof the truss attachment portions 154. Accordingly, each first flangeportion 155 a can be in surface-to-surface contact with thecorresponding second flange portion. The first and second portions 155a, 155 b can have aligned mounting holes configured to receive acorresponding fastener. The two pieces 156 a, 156 b also form thechannel 153. In a particular aspect of this embodiment, the first piece156 a and the second piece 156 b are sized so that, when placedtogether, the resulting channel 153 is slightly smaller than the crosssection of the spar around which it is placed. Accordingly, when the twopieces 156 a, 156 b are forced toward each other, the truss attachmentmember 150 can be clamped around the corresponding spar, thus securingthe truss attachment member 150 in position. For example, when secondattachment feature 151 b includes a mounting hole, the manufacturer canpass a fastener 157 through the mounting hole to both attach the trussattachment member 150 to the corresponding truss member 143 (FIG. 5A),and also clamp the truss attachment member 150 around the correspondingspar 170 (FIG. 5A).

In other embodiments, the truss attachment members 150 can be formedusing other techniques. For example, the truss attachment members 150can be extruded, molded, cast, or machined. In any of these embodiments,the truss attachment member 150 can be formed from a light-weightmaterial, e.g. a metal such as aluminum or steel, or a suitablecomposite. In other embodiments, the truss attachment members 150 can beformed from other materials that readily accommodate the attachmentfeatures 151 b. The truss attachment members 150 can be secured to thecorresponding spars using the clamping technique described above, and/orother techniques, including but not limited to adhesive bonding orco-curing.

The truss attachment members 150 can have other shapes and/orconfigurations in other embodiments. For example, the spar attachmentportion 152 need not extend around the entire circumference of thecorresponding spar 170, but can instead extend around only a portion ofthe spar 170. In some embodiments for which an adhesive joint betweenthe truss attachment member 150 and the spar 170 provides sufficientstrength, the truss attachment member 150 can have only a relativelysmall surface contacting the spar 170. The truss attachment member caninclude other numbers of truss attachment portions 154, e.g., only onetruss attachment portion 154, or more than two truss attachment portions154.

In still further embodiments, the truss attachment members 150 can beformed from other materials. For example, the truss attachment members150 can be formed from a composite material. In a particular example,the truss attachment member 150 is formed by wrapping strands (e.g.,plies of strands) around the spar 170, and overlapping the ends of thestrands (or plies) to form one or more flanges. The strands are attachedto the spar 170 with an adhesive, or via a co-curing process. Thecorresponding truss member 143 attached to the truss attachment member150 can have a slot 145 that receives the flange and is secured to theflange with an adhesive.

One feature of an embodiment of the truss attachment member 150described above with reference to FIGS. 5A-5C is that it does notrequire holes in the spar 170 to provide an attachment between the spar170 and the corresponding truss members 143. Instead, the trussattachment member 150 can be clamped or otherwise secured to the spar170 and the holes can be located in the truss attachment member 150rather than in the spar 170. This arrangement can be particularlybeneficial when the spar 170 includes composite materials, as it istypically more difficult to form mounting holes in such materials,and/or such holes may be more likely to initiate propagating fracturesand/or create stress concentrations in the spar 170.

FIGS. 5D-5F illustrate other views of the truss structure 140 describedabove with reference to FIG. 5A. FIG. 5D is a side view of a portion ofthe truss structure 140, illustrating a representative rib 142. The rib142 includes a web 146 and a flange 147 extending around the web 146.The web 146 can include one or more cut-outs 148 (three are shown inFIG. 5D) that accommodate the corresponding spars 170 a-170 c. In aparticular embodiment shown in FIG. 5D, the cut-out 148 accommodatingthe third spar 170 c can extend entirely through the thickness of therib 142. As a result, a trailing edge portion 141 of the rib 142 isdiscontinuous from the rest of the web 146 of rib 142. Accordingly, theflange 147 of the rib 142 can secure the trailing edge portion 141 ofthe rib 142 to the rest of the rib 142.

FIG. 5E is a view of the truss structure 140 from a position forward ofand above the leading edge region 117, and FIG. 5F is a view of thetruss structure 140 from a position above the trailing edge region 118.As is shown in both FIGS. 5E and 5F, the truss members can include firsttruss members 143 a and second truss members 143 b. The first trussmembers 143 a can be positioned adjacent to the web 146 of acorresponding rib 142, and can be joined to the web 146, in particular,via an adhesive or other bonding technique. Accordingly, the first trussmembers 143 a in combination with the truss attachment members 150 cansecure the ribs 142 to the spars 170 a-170 c. The second truss members143 b can extend transversely (e.g., diagonally) between neighboringribs 142 and/or spars 170 to increase the overall strength and stiffnessof the truss structure 140.

FIG. 6A is a partially schematic, side elevation view of a joint betweentwo portions 171 of a spar 170. The two portions can include a firstportion 171 a and a second portion 171 b, and the joint can be formedalong a non-monotonically varying (e.g., zig-zagging) bond line 176.Such a bond line 176 is expected to produce a stronger bond between thefirst and second portions 171 a, 171 b than is a straight or diagonalbond line. The first and second portions 171 a, 171 b may each form partof a different neighboring segment of the overall spar 170, as describedabove with reference to FIG. 2A. For example, the first portion 171 acan be part of the first segment 116 a shown in FIG. 2A, and the secondportion 171 b can be part of the second segment 116 b.

The first portion 171 a can include multiple, stacked, laminated firstlayers 172 a, and the second portion 171 b can include multiple,stacked, laminated second layers 172 b. In a particular embodiment, thelayers 172 a, 172 b can be formed from a unidirectional fiber material(e.g., fiberglass or a carbon fiber) and a corresponding resin. Each ofthe layers 172 a, 172 b can be formed from a single ply or multipleplies (e.g., six plies). The layers 172 a, 172 b can be prepreg layers,hand lay-ups, pultrusions, or can be formed using other techniques,e.g., vacuum-assisted transfer molding techniques. The first layers 172a terminate at first terminations 173 a, and the second layers 172 bterminate at second terminations 173 b. Neighboring terminations 173 a,173 b located at different positions along the thickness axis T can bestaggered relative to each other to create the zig-zag bond line 176.This arrangement produces projections 174 and corresponding recesses 175into which the projections 174 fit. In a particular aspect of thisembodiment, each layer has a termination that is staggered relative toits neighbor, except where the bond line 176 changes direction. At suchpoints, two adjacent layers can be terminated at the same location andbonded to each other, to prevent a single layer from being subjected toincreased stress levels.

During a representative manufacturing process, each of the first layers172 a are stacked, bonded and cured, as are each of the second layers172 b, while the two portions 171 a, 171 b are positioned apart fromeach other. The layers 172, 172 b are pre-cut before stacking so thatwhen stacked, they form the recesses 175 and projections 174. After thetwo portions 171 a, 171 b have been cured, the recesses 175 and/orprojections 174 can be coated and/or filled with an adhesive. The twoportions 171 a, 171 b are then brought toward each other so thatprojections 174 of each portion are received in corresponding recesses175 of the other. The joint region can then be bonded and cured.

FIG. 6B is an illustration of a spar 170 having a bond line 176generally similar to that described above with reference to FIG. 6A. Asis also shown in FIG. 6B, the spar 170 can include one or more clamps orstraps 177 that are positioned at or near the bond line 176. The clamps177 can be positioned to prevent or halt delamination that might resultbetween any of the layers in the composite spar 170. For example, asshown in FIG. 6C, if a potential delamination 178 begins between twolayers 172 a, the compressive force provided by the clamp 177 canprevent the delamination 178 from spreading further in a spanwisedirection. The clamp 177 can be positioned where it is expected that thepotential risk of delamination is high, e.g., at or near the termination173 of the outermost layers 172 a, 172 b shown in FIG. 6B. In otherembodiments, the function provided by the clamps 177 can be provided byother structures. For example, the truss attachment members 150described above can perform this function, in addition to providingattachment sites for the truss members.

FIGS. 6D-6G are a series of partially schematic, side elevation views ofspars 670 a-670 d, respectively, illustrating various joints that can beformed between adjacent spar portions 671 in accordance with otherembodiments of the disclosure. The spars 670 can be at least generallysimilar in structure and function to the spar 170 described in detailabove. For example, as shown in FIG. 6D, the spar 670 a can include afirst portion 671 a having multiple, stacked, laminated first layers 672a, and a second portion 671 b having multiple, stacked, laminated secondlayers 672 b. In addition, the first portion 671 a can be joined to thesecond portion 671 b along a bond line 676 a that is non-monotonicallyvarying (e.g., zigzagging) along the thickness axis T. In thisparticular embodiment, however, the first layers 672 a and the secondlayers 672 b have first terminations 673 a and second terminations 673b, respectively, that are not parallel to the chordwise axis C. That is,the terminations 673 are beveled or slanted relative to the chordwiseaxis C. The bevels can have the same direction and extent for eachlayer, or these characteristics can vary from one layer to the next. Forexample, as shown in FIGS. 6D and 6E in dashed lines, the layer belowthe topmost layer can be beveled in the opposite direction as thetopmost layer. Bevels in neighboring layers can be positioned directlyabove and below each other, as shown in FIGS. 6D and 6E, or the bevelsin neighboring layers can be offset in a spanwise direction so as not tooverlay each other.

Referring next to FIG. 6E, the spar 670 b can be at least generallysimilar in structure and function to the spar 670 a described in detailabove. For example, the spar 670 b can include a first portion 671 chaving multiple, stacked, laminated first layers 672 a, and a secondportion 671 d having multiple, stacked, laminated second layers 672 b.In this particular embodiment, however, the first layers 672 a havefirst terminations 673 c that form a projection 674 a, and the secondlayers 672 b have second terminations 673 d that form a recess 675 a.The projection 674 a is received in the recess 675 a to form a bond line676 b that is non-monotonically varying along both the thickness axis Tand the chordwise axis C.

Referring next to FIG. 6F, the spar 670 c is at least generally similarin structure and function to the spar 670 a described in detail above.In this particular embodiment, however, the first layers 672 a includefirst terminations 673 e, and the second layers 672 b include secondterminations 673 f, that form alternating projections 674 b and recesses675 b along the chordwise axis C. This results in a bond line 676 c thatis non-monotonically varying along the chordwise axis C but not alongthe thickness axis T.

Referring next to FIG. 6G, in this particular embodiment the firstlayers 672 a include first terminations 673 g, and the second layers 672b include terminations 673 h, that form alternating projections 674 cand recesses 675 c along the chordwise axis C, and alternatingprojections 674 d and recesses 675 d along the thickness axis T. As theforegoing discussion illustrates, there are a wide variety ofnon-monotonically varying, staggered, zigzagging, overlapping, and/orother bond lines that can be used to efficiently and strongly join sparportions together in accordance with the present disclosure.Accordingly, the present disclosure is not limited to bond lines havingany particular configuration.

One feature of embodiments described above with reference to FIGS. 6A-6Gis that they can include spar portions connected to each other along abond line that has a zig-zag shape, or otherwise varies in anon-monotonic manner. An expected advantage of this arrangement is thatthe bond line will be stronger than a simple vertical or diagonal bondline. In addition, it is expected that forming the bond line can besimplified because it does not require the use of a significant numberof additional fastening elements, and can instead employ a bondingtechnique generally similar to the technique used to bond the individuallayers of the two portions. Still further, the bond between the sparportions may be formed with no heating, or only local heating, whichavoids the need to heat the entire blade. The foregoing characteristicscan in turn facilitate the ease with which a manufacturer and/orinstaller forms a large wind turbine blade that is initially in multiplesegments (e.g., the segments 116 described above with reference to FIG.2A), which are then joined to each other, for example, at aninstallation site. Further details of suitable manufacturing techniquesare described later with reference to FIGS. 8A-16.

In other embodiments, the spar 170 can include other configurationsand/or materials. For example, selected plies can be formed from metalor carbon fiber rather than glass fiber. The plies need not all have thesame thickness. Accordingly, the dimensions and materials selected foreach ply can be selected to produce a desired strength, stiffness,fatigue resistance and cost.

FIG. 7A is a partially schematic illustration of a hub attachmentportion 112 configured in accordance with an embodiment of thedisclosure. For purposes of illustration, FIG. 7A illustrates only thehub attachment portion 112, and in particular, the transition betweenthe longitudinally extending spars 170 and a hub attachment element,e.g., a circumferentially extending hub attachment ring 180. The ring180 can include a non-composite structure, e.g., a metallic element, andcan have a relatively short spanwise direction as shown in FIG. 7A, or alonger spanwise dimension in other embodiments. The ring 180 or the hubattachment portion 112 can be circumferentially continuous, or formedfrom multiple sections arranged circumferentially. For example, the hubattachment portion 112 can include one circumferential section for eachspar 170, with each section connected to a continuous ring 180. Otherhub attachment elements that may be included in the hub attachmentregion 112 are not shown in FIG. 7A. The hub attachment portion 112 caninclude a transition to four spars 170 (as shown in FIG. 7A) or othernumbers of spars 170 (e.g., three spars 170, as shown in FIG. 3).

Each of the spars 170 can include a laminate composite of layers 172,and each of the layers 172 can in turn include multiple plies. Forexample, in a particular embodiment, each of the spars 170 can include alaminate of fifteen layers 172, each having a total of six plies, for atotal of ninety plies. Each of the plies can have fibers that areoriented unidirectionally, for example, in alignment with the spar axisS. Accordingly, such fibers have a 0° deviation from the spar axis S.The layers 172 can be stacked one upon the other, each with fibersoriented at 0° relative to the spar axis S, and can be cut so as to havethe shape shown in FIG. 7A. The number of plies oriented at 0° relativeto the spar axis S can be reduced in a direction extending toward thering 180. For example, the number of such plies can be reduced fromninety at the right side of FIG. 7A (where the spars 170 have agenerally fixed, rectangular cross-sectional shape) to twenty at thering 180 on the left side of FIG. 7A (where the structure has thinner,arcuate shape). The seventy deleted layers 172 can be terminated in astaggered fashion so that the overall thickness of the structure isgradually reduced from right to left

As the 0° orientation layers 172 are dropped off, the manufacturer canadd layers that are oriented at other angles relative to the spar axisS. For example, the manufacturer can add layers having fibers orientedat +45° and −45° relative to the spar axis S. In a particularembodiment, twenty to thirty such plies can be added, so that the totalnumber of plies at the ring 180 is between forty and fifty, as comparedwith ninety plies at the right side of FIG. 7A. By adding the +45°/−45°oriented plies to the structure at the hub attachment portion 112, theload carried by the spars 170 can be spread out in a circumferentialdirection and distributed in a more uniform fashion at the ring 180. Tofurther enhance this effect, the load path can be “steered” by providinga different number of +45° plies as compared with −45° plies. Thisarrangement can accordingly reduce or eliminate the likelihood thatindividual bolts passing through bolt holes 182 in the ring 180 willexperience significantly higher loads than other bolts located atdifferent circumferential positions. As a result, this arrangement isexpected to not only provide a smooth transition from the airfoil-shapedcross section of the blade 110 to the circular cross-section shape atthe hub attachment portion 112, but is also expected to more evenlydistribute the loads than do existing structures.

FIG. 7B is another illustration of a hub attachment portion 112 in whichthe spar 170 includes layers 172 of unidirectionally extending fibers,aligned with the spar axis S. In this embodiment, individual layers 172terminate at terminations 173. One or more termination elements 179(e.g., plates), each having a curved, fan-type shape, can be butted upagainst the spar 170, and can include recesses that receive theterminated layers 172. In a particular embodiment shown in FIG. 7B, thisarrangement includes three transition elements 179, two of which arevisible in FIG. 7B. The two visible transition elements 179 eachaccommodate multiple layers 172 (e.g., four or more layers 172). A gap183 between the two transition elements 179 receives a third transitionelement (not shown in FIG. 7B for purposes of clarity) that in turnreceives the remaining layers 172. Each of the transition elements 179can then be attached to the ring 180, which is in turn connected to apitch bearing 181. The pitch bearing 181 is used to vary the pitch ofthe wind turbine blade 110 in use. Each of the transition elements 179can have a generally arcuate cross-sectional shape where it connects tothe ring 180, and a generally flat, rectangular or rectilinearcross-sectional shape at its furthest point from the ring 180, where itconnects to the spar 170.

In other embodiments, the transition region between the hub attachmentring 180 or other attachment feature, and the rest of the blade 110 canhave other arrangements. For example, the general arrangement offan-shaped plies or plies in combination with transition elements can beapplied to other blade structures that may not include the sparsdescribed above. In another example, the arrangement of +45°/−45° pliesdescribed above can be used to “steer” loads (e.g., to more evenlydistribute loading at the boltholes 182) in blades 110 that do notinclude the spars 170, or in blades 110 that include spars or otherstructures arranged differently than is described above.

FIG. 8A is a partially schematic, side elevation view of a manufacturingassembly 801 of the turbine blade 110 configured in accordance with anembodiment of the disclosure, and FIG. 8B is an enlarged end view takenalong line 8B-8B in FIG. 8A illustrating a representative rib 142supported by a tool stanchion 802. Referring to FIGS. 8A and 8Btogether, the manufacturing assembly 801 includes a plurality of ribs142 supported by individual tool stanchions 802 at the appropriatespanwise locations. As discussed above, the turbine blade 110 includesan inboard or first blade segment 116 a, a midboard or second bladesegment 116 b, and an outboard or third blade segment 116 c. In theillustrated embodiment, the second spar 170 b (e.g., the lower or“pressure” spar) has been assembled onto the ribs 142. The spar 170 bincludes an inboard or first spar portion 871 a, a midboard or secondspar portion 871 b, and an outboard or third spar portion 871 c.

Referring next to FIG. 8B, as explained above with reference to FIG. 5D,the ribs 142 include a plurality of cutouts 148 configured to receivecorresponding truss attachment members 150. More particularly, in theillustrated embodiment the representative rib 142 includes a firstcutout 148 a configured to receive the first spar 170 a (e.g., thesuction spar; not shown in FIG. 8A or 8B), a second cutout 148 bconfigured to receive the second spar 170 b (e.g., the pressure spar),and a third cutout 148 c configured to receive the third spar 170 c(e.g., the aft spar; also not shown in FIG. 8A or 8B). As described ingreater detail below, in various embodiments one or more of the spars170 can be manufactured by laminating a plurality of prefabricatedcomposite layers or “pultrusions” together in position on themanufacturing assembly 801. Further details of these embodiments aredescribed in greater detail below with respect to FIG. 9A-16.

FIGS. 9A-9C are a series of partially schematic, enlarged isometricviews of the inboard spar portion 871 a, the midboard spar portion 871b, and the outboard spar portion 871 c configured in accordance withembodiments of the disclosure. Referring first to FIG. 9A, in theillustrated embodiment the spar 170 b can be manufactured from aplurality of layers 972 (identified individually as layers 972 a-o) thatare bonded or otherwise laminated together in place on the manufacturingassembly 801 (FIG. 8A). In particular embodiments, the layers 972 caninclude prefabricated composite materials, such as pultrusions or“planks” of pultruded composite materials. As is known, compositepultrusion is a manufacturing process that creates fiber-reinforcedpolymer or resin products having relatively consistent shape, strengthand resilience characteristics. In a typical pultruding process, thereinforcement material (e.g., unidirectional fibers, tows, roving, tapeetc. of glass fibers, aramid fibers, carbon fibers, graphite fibers,Kevlar fibers, and/or other material) is drawn through a resin bath(e.g., a liquid thermosetting resin bath of epoxy resin, vinylesterresin, polyester resin, plastic). The wet, fibrous element is thenpulled through a heated steel die, in which accurate temperature controlcures the resin and shapes the material into the desired profile. Thepultrusions can then be cut to the desired length for use. Strength,color and other characteristics can be designed into the profile bychanges in the resin mixture, reinforcement materials, die profiles,and/or other manufacturing parameters.

In the illustrated embodiment, the layers 972 can be formed frompultruded planks having generally rectangular cross sections. In oneembodiment, for example, the layers 972 can have cross-sectional widthsof from about 2 inches to about 12 inches, or from about 4 inches toabout 10 inches, and cross-sectional thicknesses of from about 0.10 inchto about 0.5 inch, or about 0.25 inch. In other embodiments, the layers972 can have other shapes and sizes. In particular embodiments, thelayers 972 can be provided by Creative Pultrusions, Inc., of 214Industrial Lane, Alum Bank, Pa. 15521. In other embodiments, the layers972 can be comprised of other types of pultruded materials as well asother types of composite materials including both prefabricated andhand-laid composite materials. In yet other embodiments, the methods ofmanufacturing turbine blade spars described herein can be implementedusing other types of laminated materials. Such materials can include,for example, wood (e.g., balsa wood, plywood, etc.), metals (e.g.,aluminum, titanium, etc.) as well as combinations of wood, metals,composites, etc.

Referring still to FIG. 9A, the inboard spar portion 871 a includes aninboard end portion 979 a and an outboard end portion 979 b. Each of theend portions includes a staggered arrangement of layers 972. Forexample, with reference to the outboard end portion 979 b, each of thelayers 972 includes a corresponding termination 973 (identifiedindividually as terminations 973 a-o) which is staggered relative toadjacent terminations 973 to form projections 974 and correspondingrecesses 975. In addition, in various embodiments the layers 972 can betapered toward the terminations 973 at the end portions 979. Asdescribed in greater detail below, this arrangement of alternatingprojections 974 and recesses 975 facilitates joining the first sparportion 871 a to the second spar portion 871 b in a very efficientoverlapping joint with a zigzag bond line.

Referring next to FIG. 9B, the second spar portion 871 b is alsocomprised of a plurality of layers 972 having terminations 973 that arestaggered to create an alternating arrangement of projections 974 andcorresponding recesses 975. Like the first spar portion 871 a, thesecond spar portion 871 b includes an inboard end portion 979 c and anoutboard end portion 979 d. As illustrated in FIG. 9B, however, thesecond spar portion 871 b becomes thinner (i.e., it tapers in thickness)toward the outboard end portion 979 d. In the illustrated embodiment,this is accomplished by successive termination of the outer layers 972as they extend outwardly from the inboard end portion 979 c. Thisgradual tapering of the spar 170 b can be done to reduce weight and/ortailor the strength of the spar 170 b for the reduced structural loadsthat occur toward the tip of the turbine blade 110.

Referring next to FIG. 9C, the third spar portion 871 c includes aninboard end portion 979 c and a corresponding outboard end portion 979f. As this view illustrates, the spar 170 b continues to taper towardthe outboard end portion 979 f by terminating various layers 972 as theyapproach the end portion 979 f.

FIGS. 9D and 9E include partially schematic, enlarged side viewsillustrating additional details of the first spar portion 871 a and thesecond spar portion 871 b configured in accordance with an embodiment ofthe disclosure. In addition, these Figures also illustrate variousfeatures of the end portions of some of the layers 972. As shown in FIG.9D, the outboard end portion 979 b of the first spar portion 871 aincludes a plurality of alternating projections 974 and correspondingrecesses 975 formed by the staggered terminations 973 of the respectivelayers 972. As this view further illustrates, the end portions of thelayers 972 can be gradually tapered toward the termination 973 tofurther facilitate and shape the projections 974/recesses 975 intogradually transitioning recesses/projections. For example, in theillustrated embodiment, the last 2 to 6 inches, or about the last 4inches of each layer 972 can have a double-sided taper (if, e.g., aninner layer 972) or a single-sided taper (if, e.g., an outer layer 972)to a termination 973 of from about 0.0 inch to about 0.07 inch, or about0.04 inch.

Referring next to FIG. 9E, the inboard end portion 979 c of the secondspar portion 871 b includes a plurality of projections 974 configured tofit into corresponding recesses 975 of the outboard end portion 979 b ofthe first spar portion 871 a. Similarly, the inboard end portion 979 calso includes a plurality of recesses 975 configured to receivecorresponding projections 974 of the outboard end portion 979 b of thefirst spar portion 871 a. For example, during manufacture of the spar170 b, the first projection 974 a on the outboard end portion 979 b ofthe first spar portion 871 a is fit into the corresponding first recess975 a on the inboard end portion 979 c of the second spar portion 871 b.Although the respective end portions 979 are fit together in this mannerduring assembly of the spar 170 b on the manufacturing assembly 801 ofFIG. 8A, the mating end portions 979 are not actually bonded together atthis time, so that the blade sections 116 (FIG. 8A) can be separatedafter manufacture and individually transported to the installation site.

As shown in FIG. 9F, when the outboard end portion 979 b of the firstspar portion 871 a is ultimately joined to the inboard end portion 979 cof the second spar portion 871 b at the installation site, thealternating projections 974 and recesses 975 create an overlapping or azigzag bond line 976. As is known to those of ordinary skill in the art,this is a very efficient structural joint, and can avoid or at leastreduce the need for further structural reinforcement of the jointbetween the first spar portion 871 a and the second spar portion 871 b.

FIGS. 10A and 10C-10E are a series of partially schematic side elevationviews of a portion of the manufacturing assembly 801 of FIG. 8A,illustrating various stages in a method of manufacturing the spar 170 bin situ on the truss structure of the turbine blade 110 in accordancewith an embodiment of the disclosure. FIG. 10B is an enlarged end viewtaken along line 10B-10B in FIG. 10A, further illustrating aspects ofthis spar manufacturing method. Referring first to FIGS. 10A and 10Btogether, the ribs 142 have been secured to their corresponding toolstanchions 802, and a plurality of truss members 143 have been installed(at least temporarily) between corresponding truss attachment members150. Each truss attachment member 150 of the illustrated embodimentincludes a first piece 1056 a and a mating second piece 1056 b. As shownin FIG. 10A, only the first piece 1056 a is attached to the trussstructure during build-up of the spar 170 b. As discussed in more detailbelow, after all of the spar layers 772 have been properly arranged onthe first piece 1056 a of the truss attachment member 150, the secondpiece 1056 b is fit into position and secured to the first piece 1056 a.

Referring next to FIG. 100, the individual spar layers 772 aresequentially placed into position on the first piece 1056 a of the trussattachment member 150 of each rib 142. As the spar layers 772 are placedon top of each other, the terminations 773 are positioned as shown inFIGS. 7A-7E to produce the desired spar profile. A layer of adhesive(e.g., epoxy adhesive, thermosetting resin adhesive, etc.) can beapplied to one or both of the mating surfaces of adjacent layers 772.The spar layers 772 can be temporarily held in position during thestacking process with clamps 1002 (e.g., C-clamps and/or other suitableclamps known in the art).

Referring next to FIG. 10D, once all of the layers 772 have beenproperly arranged on the first pieces 1056 a of the truss attachmentmembers 150, the layers 772 can be compressed during the adhesive curingcycle using a suitable clamping tool, such as the compressing apparatus1090 described in greater detail below. More particularly, a pluralityof the compressing apparatuses 1090 can be positioned on the sparportion 871 between the ribs 142 to compress the layers 972 togetherduring the curing process. The compressing apparatus 1090 is describedin greater detail below with reference to FIGS. 12A-15.

Referring next to FIG. 10E, once the adhesive between the layers 972 hascured, the second pieces 1056 b of each of the truss attachment members150 can be installed on the truss structure and joined to thecorresponding first pieces 1056 a with threaded fasteners and/or othersuitable methods. In one embodiment, adhesive can be applied between themating surfaces of the first piece 1056 a and the spar portion 871,and/or the second piece 1056 b and the spar portion 871, to bond thespar portion 871 to the respective truss attachment members 150. Inother embodiments, such adhesive can be omitted.

FIG. 11A is an enlarged isometric view of a portion of the trussstructure of the turbine blade 110, and FIG. 11B is an end view of arepresentative rib 142 illustrating aspects of the installed spars 170.In one embodiment, the second piece 1056 b of the truss attachmentmember 150 can be mated to the first piece 1056 a by sliding the secondpiece 1056 b sideways into the cutout 148. For this procedure, the endportions of the truss members 143 can be temporarily detached fromcorresponding truss attachment portions 1154 of the truss attachmentmember 150. Once both pieces 1056 of the truss attachment member 150 arein their respective positions, the end portions of the truss members 143can be rejoined to the truss attachment portions 1154. In oneembodiment, the end portions of the truss members 143 and thecorresponding truss attachment portions 1154 can be pilot drilledundersize, and then drilled full size during final assembly. Moreover,the end portions of the truss numbers 143 can be attached to the trussattachment portions 1154 by fasteners 859 that are frozen beforeinstallation in the corresponding fastener holes so that they expand toa press fit after installation. In other embodiments, the truss members143 can be attached to the truss attachment members 150 using othersuitable methods known in the art.

FIG. 11C is a partially schematic isometric view of a portion of themanufacturing assembly 801 after the spar 170 b has been fully assembledand installed on the truss structure of the turbine blade 110. Referringto FIGS. 11A and 11C together, although the mating end portions 979 ofthe second spar portion 871 b and the third spar portion 871 c areassembled in place to ensure that they will fit neatly together duringfinal assembly, the end portions 979 are not bonded during trussmanufacture. This enables the second blade section 116 b and the thirdblade section 116 c to be separated from each other at the manufacturingfacility for transportation to the installation site. Accordingly, inthe illustrated embodiment the end portions 979 of the spar portions 871are not bonded together during the manufacturing process, but insteadform separation joints 1120 where the spars 170 will be joined togetherwhen the turbine blade 110 is assembled on site. In one embodiment, thespars can be joined together on site using the systems and methodsdescribed in detail in U.S. Provisional Patent Application No.61/180,816, filed May 22, 2009 and incorporated herein in its entiretyby reference. The blade segments can be transported to the site usingsystems and methods described in detail in U.S. Provisional PatentApplication No. 61/180,812, filed May 22, 2009 and incorporated hereinin its entirety by reference.

FIG. 12A is an isometric view of the compressing apparatus 890configured in accordance with an embodiment of the disclosure, and FIG.12B is a partially exploded isometric view of the compressing apparatus1090. Referring to FIGS. 12A and 12B together, the compressing apparatus1090 includes a first tool portion 1250 a and a second tool portion 1250b. In the illustrated embodiment, the tool portions 1250 are mirrorimages of each other, or are at least very similar to each other. Eachtool portion 1250 includes a support plate 1254 and opposing sideflanges 1256 (identified individually as a first side flange 1256 a anda second side flange 1256 b) extending therefrom. As described ingreater detail below, the tool portions 1250 are configured to fittogether in a clamshell arrangement around a portion of the laminatedspar 170 to compact and compress the spar layers (e.g., the layers 772)together while the adhesive between the layers cures. More particularly,each of the tool portions 1250 includes one or more expandable members1258 configured to expand inwardly from the support plate 1254 tothereby compress the corresponding spar section during the curingprocess. In the illustrated embodiment, the first side flange 1256 a issomewhat wider than the second side flange 1256 b, so that the matingflanges 1256 can overlap and be temporarily held together with fasteners1252 (e.g., threaded fasteners, such as bolts, screws, etc.) during thecompressing and curing process. Each tool portion 1250 can also includea first end portion 1261 and an opposing second end portion 1262.Handles 1253 can be provided on the end portions 1261 and 1262 tofacilitate manual placement, installation and/or removal of the toolportions 1250. The tool portions 1250 can be manufactured from variousmaterials having sufficient strength, stiffness, and manufacturingcharacteristics. For example, in one embodiment the tool portions 1250can be formed from aluminum that is machined, welded, or otherwiseformed to the desired shape. In other embodiments, the tool portions1250 can be fabricated from other suitable metals including steel,brass, etc., as well as suitable non-metallic materials such ascomposite materials.

FIG. 13A is an exploded isometric view of the first end portion 1261 ofthe first tool portion 1250 a, and FIG. 13B is an enlarged isometricview of the second end portion 1262. Referring first to FIG. 13A, eachtool portion 1250 includes a manifold 1360 for filling and unfilling theexpandable members 1258 with a fluid (e.g., compressed air). In theillustrated embodiment, a conduit 1368 (identified individually asconduits 1368 a-c) extends between each expandable member 1258 and afill/drain fitting 1366. The fill/drain fitting 1366 can include athreaded orifice 1370 or other feature (e.g., a high-pressure aircoupling) configured to receive a corresponding fitting for flowingfluid into the respective expandable members 1258 through the conduits1368. In one embodiment, for example, the expandable members 1258 can befilled with compressed air to inflate the expandable members 1258 andthereby compress the layers of the spar 170 together during the curingcycle. In other embodiments, the expandable members 1258 can be filledwith other types of gas or liquids (e.g., water, oil, etc.) to inflatethe expandable members 1258 and compress the spar layers together.

The proximal end portions of the expandable members 1258 can include anend closure 1364 to seal the expandable member 1258 and maintainpressure. In the illustrated embodiment, the end closures 1364 caninclude two or more plates that sandwich the end portion of theexpandable member 1258 therebetween to prevent leakage. In otherembodiments, other structures and systems can be used to seal theproximal end portions of the expandable members 1258. As shown in FIG.13B, the distal end portions of the expandable members 1258 can beclosed off and sealed with a suitable end closure plate 1365 that isfastened to the support plate 1254 with a plurality of fasteners 1352.In other embodiments, the end portions of the expandable members 1258can be secured to the tool portion 1250 and/or closed off and sealedusing other suitable means.

FIG. 14A is an enlarged isometric view of the second tool portion 1250b, and FIG. 14B is a partially exploded isometric view of the secondtool portion 1250 b. With reference to FIG. 14B, each of the expandablemembers 1258 can include a flexible tubular structure comprised of anouter layer 1430 and an inner layer 1432. The outer layer 1430 caninclude a suitable material to provide strength to the expandable member1258, and the inner layer 1432 can include a suitable material forsealing the expandable member 1258. For example, the inner sealing layer1432 can include a rubber liner, and the outer layer 1430 can includewoven nylon, fiberglass, etc. Accordingly, in one embodiment theexpandable member 1258 can include a structure that is at leastgenerally similar in structure and function to a fire hose. In otherembodiments, the expandable members 1258 can include other materials andhave other structures.

FIG. 15 is an enlarged end view taken substantially along line 15-15 inFIG. 10D illustrating use of the compressing apparatus 1090 inaccordance with an embodiment of the disclosure. In this view, the sparlayers 972 have been appropriately positioned on the truss substructure,with bonding adhesive between the layers. The first tool portion 1250 ahas been positioned on one side of the spar 170, and the second toolportion 1250 b has been positioned on the other side. Each first flange1256 a of each tool portion 1250 overlaps the corresponding secondflange 1256 b of the opposing tool portion 1250. Once the two toolportions 1250 have been properly positioned, the tool portions 1250 aretemporarily attached with the fasteners 1252. A pressure source (e.g. asource of compressed air) is then attached to the manifold 1360 on eachtool portion 1250, and the expandable members 1258 are inflated to asufficient pressure. As they expand, the expandable members 1258 providean even, distributed pressure over the laminated spar 170. The pressurecan be modulated as required to provide a desired level of compactionand compression during the curing process. Moreover, a suitable vacuumbag or other thin film protective layer can be wrapped around the spar170 to avoid getting adhesive on the compressing apparatus 1090. Afterthe spar 170 has suitably cured, the compressing apparatus 1090 can bedisassembled by relieving the pressure in the expandable members 1258and removing the fasteners 1252.

The methods and systems described in detail above can be used toassemble a wind turbine blade spar in situ on a manufacturingsubassembly in accordance with embodiments of the disclosure. Moreparticularly, several embodiments of the disclosure have been describedin detail above for manufacturing laminated spars using pultrudedcomposite materials, such as pultruded composite “planks.” There are anumber of advantages associated with some of these embodiments. Theseadvantages can include, for example, lower cost and lower weight windturbine blades as compared to conventional manufacturing techniques.Moreover, use of pultrusions can reduce dimensional variations in thefinished parts.

In certain embodiments, other turbine blade structures, such as outerskins, ribs, truss members, etc. can be formed from pultruded compositematerials. For example, in one embodiment skins can be formed from oneor more pultruded composite members (e.g., sheets) that are laminatedtogether. In other embodiments, truss members can be formed fromcomposite pultrusions. Accordingly, the methods and systems disclosedherein for forming turbine blade structures from pultruded materials arenot limited to use with turbine blade spars or spar caps, but can beused to form other turbine blade structures.

In other embodiments, however, turbine blade spars and/or other bladestructures, such as the spars 170 described herein, can be manufacturedfrom pultruded composite materials using a suitable production tool.FIG. 16, for example, illustrates a tool 1610 having a mold surface 1612with an appropriate contour for the spar 170 b. To manufacture the spar170 b on the tool 1610, the layers 972 (e.g., pultruded planks) aresequentially positioned on the mold surface 1612. Tooling pins 1614and/or other locaters can be used to accurately position the layers 972.The layers 972 can be precut to the appropriate lengths so that whenarranged on the tool surface 1612, the respective end portions 979 formthe desired zigzagging joint or overlapping fingers. Although noadhesive is used between the mating end portions 979 at this time, eachlayer 972 is covered with adhesive prior to installation on the tool1610. After all the layers 972 have been placed on the tool surface1612, the lay up can be vacuum-bagged to extract the air from thelaminate and compress the layers 972 together. The spar can be cured atroom temperature, or heat can be applied via an autoclave or other meansif desired for the particular adhesive used.

From the foregoing, it will be appreciated that specific embodimentshave been described herein for purposes of illustration, but that theinvention maybe include other embodiments as well. For example, featuresdescribed above with reference to FIG. 7A in the context of fourspanwise extending spars can be applied to wind turbine blades havingother numbers of spars, including three spars. In addition, the trussstructures described above can have arrangements other than thosespecifically shown in the Figures. The attachments between spars, ribs,and truss members can have arrangements other than those describedabove. Certain aspects of the disclosure described in the context ofparticular embodiments may be combined or eliminated in otherembodiments. Further, while advantages associated with certainembodiments have been described in the context of those embodiments,other embodiments may also exhibit such advantages, and not allembodiments need necessarily exhibit such advantages to fall within thescope of the disclosure. Accordingly, the invention can include otherembodiments not explicitly shown or described above. Therefore, theinvention is not limited, except as by the appended claims.

1. A wind turbine blade, comprising: an external aerodynamic surfacehaving a longitudinally-extending spanwise axis, a chordwise axisextending transverse to the spanwise axis, and a thickness axisextending transverse to both the chordwise and spanwise axes; and aplurality of longitudinally-extending spars providing internal supportfor the aerodynamic surface, wherein at least one of the spars includesa laminate of precured composite material, the laminate of precuredcomposite material including: a plurality of precured composite layers;and a plurality of adhesive layers interposed between adjacent precuredcomposite layers.
 2. The wind turbine blade of claim 1 wherein each ofthe precured composite layers includes a precured fiber-reinforced resinproduct.
 3. The wind turbine blade of claim 1 wherein each of theprecured composite layers includes a precured composite pultrusion. 4.The wind turbine blade of claim 1 wherein the aerodynamic surfacedefines an airfoil cross-section, wherein the plurality oflongitudinally-extending spars include a pressure spar and a suctionspar spaced apart from each other along the thickness axis, and an aftspar spaced apart from both the pressure and suction spars along thechordwise axis, and wherein each of the pressure, suction and aft sparsare comprised of a laminate of precured composite pultrusions.
 5. Thewind turbine blade of claim 1, further comprising a plurality oflongitudinally spaced-apart ribs, and wherein the at least one spar isattached to the ribs.
 6. The wind turbine blade of claim 1, furthercomprising a strap clamped circumferentially around the plurality ofprecured composite layers.
 7. The wind turbine blade of claim 1, furthercomprising: a plurality of longitudinally spaced-apart ribs; and aplurality of truss attachment members, wherein each of the trussattachment members includes a first piece and a corresponding secondpiece, wherein each of the first pieces is attached to the correspondingsecond piece to clamp a portion of the precured composite layerstogether therebetween, and wherein at least one of the first piece andthe second piece of each truss attachment member is attached to one ofthe longitudinally spaced apart ribs.
 8. An apparatus for compressing aplurality of precured composite material layers together for lamination,the apparatus comprising a first tool portion including: a first supportbase; a first expandable member carried by the first support base; and afirst fitting in fluid communication with the first expandable member;and a second tool portion including: a second support base; a secondexpandable member carried by the second support base; and a secondfitting in fluid communication with the second expandable member,wherein the second support base is configured to be operably coupled tothe first support base with the plurality of composite material layerspositioned between the first and second expandable members, and whereinthe first and second fittings are configured to transfer fluid into thefirst and second expandable members to expand the expandable members andcompress the composite material layers therebetween.
 9. The apparatus ofclaim 8 wherein the first and second tool portions are configured to befit together in a clamshell arrangement around the composite materiallayers.
 10. The apparatus of claim 8 wherein the first tool portionincludes first and second side flanges extending outwardly from oppositesides of the first support base, wherein the second tool portionincludes third and forth side flanges extending outwardly from oppositesides of the second support base, and wherein the first side flange isconfigured to overlap the third side flange, and the second side flangeis configured to overlap the fourth side flange, when the first toolportion is operably coupled to the second tool portion with theplurality of composite material layers positioned therebetween.
 11. Theapparatus of claim 8: wherein the first tool portion further comprises:at least a third expandable member positioned adjacent to the firstexpandable member; and a first manifold extending from the fitting tothe first and third expandable members; and wherein the second toolportion further comprises: at least a fourth expandable memberpositioned adjacent to the second expandable member; and a secondmanifold extending from the fitting to the second and fourth expandablemembers, wherein the first fitting is configured to transfer fluid intothe first and third expandable members via the first manifold to expandthe first and third expandable members against one side of the compositematerial layers, and wherein the second fitting is configured totransfer fluid into the second and fourth expandable members via thesecond manifold to expand the second and fourth expandable membersagainst the opposite side of the composite material layers to compressthe composite material layers therebetween.
 12. A method ofmanufacturing a wind turbine blade, the method comprising: moving fibersthrough a resin bath to wet the fibers with resin; moving the wet fibersthrough a heated die to cure the resin and shape the resin and fibersinto an elongate composite pultrusion; cutting the elongate compositepultrusion into individual pieces to form a plurality of pultrudedcomposite pieces; laminating the plurality of pultruded composite piecestogether to form a first wind turbine blade structure; and attaching thefirst wind turbine blade structure to a second wind turbine bladestructure to form a portion of a wind turbine blade truss structure. 13.The method of claim 12 wherein laminating the plurality of pultrudedcomposite pieces together to form a first wind turbine blade structureincludes forming an elongate spar.
 14. The method of claim 12 whereinthe wind turbine blade includes an external aerodynamic surface having alongitudinally-extending spanwise axis, a chordwise axis transverse tothe spanwise axis, and a thickness axis transverse to both the chordwiseand spanwise axes, wherein laminating the plurality of pultrudedcomposite pieces together to form a first wind turbine blade structureincludes forming a spar portion, and wherein attaching the first windturbine blade structure to a second wind turbine blade structureincludes orienting the spar portion along the spanwise axis and fixedlyattaching the spar portion to a plurality of ribs extending along thechordwise axis.
 15. The method of claim 12: wherein the wind turbineblade includes an external aerodynamic surface having alongitudinally-extending spanwise axis, a chordwise axis transverse tothe spanwise axis, and a thickness axis transverse to both the chordwiseand spanwise axes; wherein laminating the plurality of pultrudedcomposite pieces together to form a first wind turbine blade structureincludes laminating a first plurality of pultruded composite layerstogether to form a first spar portion having a first spar end portionwith a plurality of first projections and first recesses along thechordwise axis, and laminating a second plurality of pultruded compositelayers together to form a second spar portion having a second spar endportion with a plurality of second projections and second recesses alongthe chordwise axis; and wherein attaching the first wind turbine bladestructure to a second wind turbine blade structure includes insertingindividual first projections into corresponding second recesses, andinserting individual second projections into corresponding firstrecesses, to join the first spar end portion to the second spar endportion.
 16. A method of manufacturing a wind turbine blade having anexternal aerodynamic surface with a longitudinally-extending spanwiseaxis, a chordwise axis transverse to the spanwise axis, and a thicknessaxis transverse to both the chordwise and spanwise axes, the methodcomprising: positioning a plurality of turbine blade ribs in amanufacturing assembly, wherein individual ribs are aligned with thechordwise axis and are spaced apart from each other along the spanwiseaxis; positioning a first elongate layer of composite material acrossthe plurality of ribs along the spanwise axis; applying a layer ofadhesive to the first layer of composite material; positioning a secondelongate layer of composite material on the layer of adhesive;compressing the first and second elongate layers of composite materialtogether; and curing the adhesive to laminate the second layer ofcomposite material to the first layer of composite material and form aspar portion extending along the spanwise axis between the plurality ofribs.
 17. The method of claim 16 wherein positioning a first elongatelayer of composite material across the plurality of ribs includespositioning a first layer of precured composite material across theribs, and wherein positioning a second elongate layer of compositematerial on the layer of adhesive includes positioning a second layer ofprecured composite material on the layer of adhesive.
 18. The method ofclaim 16 wherein positioning a first elongate layer of compositematerial across the plurality of ribs includes positioning a firstpultruded layer across the ribs, and wherein positioning a secondelongate layer of composite material on the layer of adhesive includespositioning a second pultruded layer on the layer of adhesive.
 19. Themethod of claim 16 wherein each of the individual ribs includes acutout, and wherein positioning a first elongate layer of compositematerial across the plurality of ribs includes positioning portions ofthe first elongate layer of composite material into each of the cutouts.20. The method of claim 16 wherein each of the individual ribs includesa cutout, and wherein the method further comprises: positioningindividual fittings in each of the individual cutouts; attaching theindividual fittings to the corresponding ribs; and attaching acorresponding portion of the spar portion to each of the individualfittings.
 21. The method of claim 16, further comprising: positioning aplurality of additional elongate layers of composite material on thefirst and second elongate layers; and terminating the individual layersof composite material at different longitudinal locations to form a sparend portion having a plurality of projections and recesses, withindividual projections alternating with individual recesses along thethickness axis.
 22. The method of claim 16 wherein curing the adhesiveto laminate the second layer of composite material to the first layer ofcomposite material and form a spar portion includes forming a spar endportion having a plurality of projections and recesses, with individualprojections alternating with individual recesses along the chordwiseaxis.
 23. The method of claim 16 wherein the plurality of turbine bladeribs is a plurality of first turbine blade ribs, wherein curing theadhesive to laminate the second layer of composite material to the firstlayer of composite material and form a spar portion includes forming afirst spar portion having a first spar end portion with a plurality offirst projections and first recesses, and wherein the method furthercomprises: positioning a plurality of second turbine blade ribs in asecond manufacturing assembly, wherein individual second ribs arealigned with the chordwise axis and are spaced apart from each otheralong the spanwise axis; positioning a third elongate layer of compositematerial across the plurality of second ribs along the spanwise axis;applying a second layer of adhesive to the third layer of compositematerial; positioning a fourth elongate layer of composite material onthe second layer of adhesive; compressing the third and fourth elongatelayers of composite material together; curing the second layer ofadhesive to laminate the third layer of composite material to the fourthlayer of composite material and form a second spar portion extendingalong the spanwise axis between the plurality of second ribs, the secondspar portion including a second spar end having a plurality of secondprojections and second recesses; applying adhesive to the first spar endportion and the second spar end portion; inserting individual firstprojections into corresponding individual second recesses, and insertingindividual second projections into corresponding first recesses, to jointhe first spar portion to the second spar portion.
 24. The method ofclaim 16 wherein compressing the first and second elongate layers ofcomposite material together includes: removably coupling a plurality ofcompressing apparatuses to the first and second layers of compositematerial between individual turbine blade ribs; and operating thecompressing apparatuses to compress the first and second layers ofcomposite material together.
 25. The method of claim 16 whereincompressing the first and second elongate layers of composite materialtogether includes: positioning a first tool portion on one side of thefirst and second layers of composite material, the first tool portionhaving an expandable member; positioning a second tool portion on theopposite side of the first and second layers of composite material;coupling the first tool portion to the second tool portion; andexpanding the expandable member to compress the first and second layersof composite material together.
 26. The method of claim 16 whereincompressing the first and second elongate layers of composite materialtogether includes: positioning a first tool portion on one side of thefirst and second layers of composite material, the first tool portionhaving an expandable member; positioning a second tool portion on theopposite side of the first and second layers of composite material;coupling the first tool portion to the second tool portion; andinflating the expandable member to compress the first and second layersof composite material together.
 27. The method of claim 16 whereincompressing the first and second elongate layers of composite materialtogether includes: positioning a first tool portion on one side of thefirst and second layers of composite material, the first tool portionhaving a first expandable member; positioning a second tool portion onthe opposite side of the first and second layers of composite material,the second tool portion having a second expandable member; coupling thefirst tool portion to the second tool portion; and expanding the firstand second expandable members to compress the first and second layers ofcomposite material together.